"AN ELECTRICAL IMPULSE GENERATOR"

Abstract

A integrated flue support construction (2) for a Marx impulse voltage generator (2) with several generator stages (3} is disclosed. It has been known to arrange a flue (2) for flushing the air of switching spark gaps (4) separately from a support frame for the switching spark gaps (4), the impulse capacitors (5) and series and parallel resistors (7,8) .According to the invention/ the flue (2) has a supporting function for the switching spark gaps (4) and individual or all electrical components (5-10) of the impulse circuit. In one embodiment the flue (2) consists of a triangular cylinder support structure (2), wherein the side walls (11) are formed by insulating plates (11), each receiving one of the electrical components, namely the switching spark gap (4), impulse capacitor (5) and resistors (7, 8). Advantages of the invention are : A less complicated construction and a saving of costs, a more compact design with smaller flue cross sectional area (22) and thereby smaller self-inductance of the impulse circuit as well as easier production, transportability and handling because of stacked modules (14) each with at least one generator stage (3).

Full Text

separately and laterally from the support structure, which encloses the switching discharge gaps arranged on top of each other and has an air inlet opening with a ventilator at its bottom end and an air outlet opening it its top end. The flue can be designed as a insulating tube and may be provided with viewing windows for the spark discharge gaps. The additional construction effort and costs are disadvantageous. On the one hand, the support structure of the impulse voltage generator must be designed for additionally holding the flue. On the other hand, the spark discharge gaps must be located, in com-parison, separately from the other components of the impulse generator in order to guarantee sufficient insulation spac-ings between the wal1 of the flue and the spark discharge gaps. The area enclosejd by the discharge circuit is thereby increased and the switching performance is impaired by in-creased self-inductance.
An individual housing of each separate discharge gap is e.g. realized by the company Passoni & Villa. Each housing is fed individually with filtered air and an air ex-change is achieved due to leaks. The room required for hous-ing each generator stage as well as the feeding tubes for pressurised air cause again a substantial additional effort.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved electrical impulse generator where spontaneous dis-charges of the discharge gaps are suppressed with small addi-tional effort. This object is achieved by the features of the independent claim.
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The solution according to the invention consists in an electrical impulse generator, in particular suited for generating high impulse voltages or impulse currents, which comprises a support frame for at least one chargeable genera-tor stage, which comprises a switching discharge gap for gen-erating electrical discharges in a gaseous medium and further electrical components for charging and/or discharging the generator stage, wherein the switching discharge gap is ar-ranged in a flue with a defined gas exchange for controlling and/or keeping constant the dielectric strength of the gase-ous medium, wherein further the flue is designed as a support structure and the support structure has a supporting function for the switching spark gap and for at least one of the electrical components of the at least one chargeable generator stage. By the integration of supporting functions into the flue, the constructive effort required for a conventional support structure can be reduced or eliminated. This allows substantial savings of costs.
In one embodiment, the flue has a supporting function for at least one impulse capacitor and/or at least one series resistor, parallel resistor, charging resistor and/or potential resistor of the at least one chargeable gen-erator stage. In particular the flue forms the supporting frame for all generator stages of the impulse generator.
In another embodiment, the flue is an insulating tube with a polygonal or round cross section and the electri-cal components of each generator stage, in particular an im-pulse capacitor, a series resistor and a parallel resistor, can be attached to the side walls of the insulating tube. In this manner, an interior flue is created and a very simple and compact construction of the impulse generator is achieved.
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In a further embodiment, the insulating cube has a small cress section area for creating a low i nductance spark current circuit with a small enclosed area. By the in-tegrated flue and support structure it is in fact possible to lower the inductance of the discharge circuit to values Chat have so far been unknown for housed impulse generators, and the electrical switching characteristics can corrasponding1y be improved. Advantageously, the insulating tube is designed to be assembled from modules that can be stacked on top of each other, wherein the modules comprise at least one genera-tor stage, preferably two, three or four generator stages. The modular construction makes an efficient prefabrication at the factory possible, as well as a fast and easy final assembly at the customer. The impulse generator can be adapted to different desired high voltage or high current values quickly and flexibly by adding or removing modules. The modularity is therefore also of great advantage to the user during operation .
In a further embodiment, the flue is built from insulating plates assembled into a triangular cylinder assem-bly, and each side wall comprises mounting holes either for mounting the spark discharge gap, or an impulse capacitor or two mounting arms for receiving a series resistor and a par-allel resistor, respectively. The triangular cylinder con-struction can be manufactured easily and has a very small en-closed induction area of the discharge circuit.
Further embodiments, advantages and applications of the invention result from the dependent claims as well as from the now following description, which makes reference to the figures.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. shows a supporting flue structure accorci-ing to the invention for an impulse generator in cross sec-tion; and
Fig. 2 shows the flue structure of Fig. 1 in a side view.
In the figures, similar parts are designated with the same reference numerals.
DETAILED DESCRIPTION OF THE INVENTION
Fig. 1 shows the cross section of a generator
stage 3 of an electrical impulse generator 1 and in particu-lar of a Marx impulse generator 1 for generating pulse shaped high voltages. In the shown generator stage 3 there are il-lustrated a switching spark gap 4, an impulse capacitor 5 and mounting arms 6 for snapping in at least one parallel resis-tor S into generator stage 3 and of at least one scries re-sistor 7 between two generator stages 3 arranged on top of each other. Switching spark gap 4 comprises two discharge electrodes 4b, which are typically rounded. The commonly known principle of operation is based on charging the at least one impulse capacitor 5 in several generator stages 3 in parallel via charging resistors 9 and on discharging the capacitors via the series resistors 7 and the parallel resis-tors 8 in a series circuit in puiaea manner. In a manner that is, per se, known, the series resistors 7, also called front or damping resistors 7, serve to control the impulse rise times and the parallel resistors 8 to control the impulse de-cay times. Potential resistors 9 can be present for achieving a more homogenous voltage distribution and/or for safely re-
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moving residual charges of the housings of the impulse ca-pacitors 5. Impulse capacitor 4 comprises lead-throughs 5b for its high voi tage terminals 5a, which are typically de-signed for 103 or 200 kV at sach generator stage 3. The ter-minals 5a are connected to the terminals 4a of the switching spark gaps and the support arms 6 of the resislors 7 , 8 in high voltage proof manner by means of cable connections or such of minimum length. The side walls 11 form a support structure 2 for switching spark gap 4 and the electrical com-ponents 5 - 10 of generator stage 3. In addition to this, the side walls 13 form a laterally enclosed space 22, which serves as a flue 2 for exchanging air for switching spark gap 4 located inside flue 2. Air, dried air or another fluid, such as a protective gas, can be led through flue 2 in order to keep the dielectric strength of switching spark gap 4 con-stant or t increase it as compared to environmental air. In particular, particles floating in air, dust, burn-off or ozone of previous discharge processes are flushed out of the regions of the switching spark gaps 4 by means of flue 2. Flue 2 according to the invention therefore combines the function of a controlled air exchange and the support func-tion for the electrical components 5 - 10.
In the embodiment of Fig. 1, a particularly compact design is achieved by a triangular cylindrical flue support structure 2. The triangular shape 2 corresponds to a close or even minimum distance of switching discharge gap 4, an impulse capacitor 5 and the resistors 7, 3, wherein the flat side walls 11 arc especially suited for a simple mounting of the electrical components 5 9. Other polygonal flue cross sections 2 are possible as well and may e.g. be useful if several impulse capacitors 5 per generator stage 3 or additional auxiliary spark gaps (not shown) are present. Advantageously, in each generator stage 3, an impulse capacitor 5,
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a series resistor 7, a parallel resistor 8 and/or a discharge resistor 9 are arranged outside flue 2 and comprise contacts or lead-throughs 5b into the interior of flue 22. In this manner, the electrical components 5-9 and in particular the resistors 7-9 can be, exchanged very easily and are well visible from the outside. In particular, the value of the resistors can by checked due to a characteristic coloring. A drive 4d for adjusting the switching spark gaps 4 can be arranged in flue 2. Flue 2 can be provided with viewing windows 4c for the witching spark gaps 4, which serve, in a per-se known manner, for visual control and, where applicable, for an optical synchronization and thereby easier firing of the air in switching spark gap 4. 3y means of the presented triangular cylinder design 2 a pulse wave or discharge current circuit of very small cross section or enclosed section 22 and therefore low self induction can be achieved.
With the integration flue support structure 2 with an internal flue anterior 22 a support structure 2 is created that is very stable, compact, easy to manufacture and easy to handle, for several or all generator stages 3 of an impulse generator 1. Impulse generator 1 can also be an impulse current generator 1 built in similar manner. Conventional support structures with support tubes and steel frame or intermediate connecting plates for laterally mounting the support tubes can therefore be simplified or, as shown, be dispensed with completely. The flue support structure 2 can, where applicable, be further laterally stabilized by lateral bracing with glass fiber cables or such.
In the given embodiment the triangular cylinder construction 2, i.e. the tube or hollow cylinder 2 with triangular cross section, is built from insulating plates forming the side walls 11, which comprise mounting holes for mounting the electrical components 4 - 9. The insulating
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plates 11 are joined by metallic bracket members 11a contacting adjacent terminals 4a, 5a, 6a of the electrical components 4-9 via leads 11b or similar. Two side walls 11 of the triangular cylinder construction 2 comprise, in the region of the impulse capacitor 5, projecting parts 12, each having at least one suspension opening 13. in particular, a connecting line through the support holes 13 runs substantially through a center of mass of the impulse generator 1 such that the impulse generator 1 or an individual generator module 14 can be lifted and transported very easily and without lateral tiling by means of a lifting tool engaging the support holes.
Fig. 2 shows the flue support structure 2 in a lateral view. The triangular polygonal or round insulating tube 11 is shown to be assembled from modules 14 stacked on top of each other. In the case of triangular cylinder modules 14, for example, stackability can be implemented, by providing the cylinder modules 14 with projecting centering members (not shown) arranged in staggered relation to a side wall 11, in particular by centering pins glued or mounted to the bracket members lla..In general, a centering frame for stacking the cylindrical modules 14 can be present as well. Each module 14 comprises at lest one generator stage 3 and preferably two, three or four generator stages 3, Cylinder modules 14 can also be used with arbitrary other flue cross section geometries. The bottommost module 14 should have an air entry opening 15a with a ventilator and the topmost module 14 an air exit opening 15b. Air entry and air exit can also be exchanged. The support structure and the flue 2, In particu-lar a flue 2 forming the support structure, can also be mounted on a displaceable frame 16, in particular on a wheeled vehicle or an air-cushioned vehicle.
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1. Electrical impulse generator (1), in particular suited for generating high impulse voltages or impulse currents, comprising a flue (2) formed by a support structure for at least one chargeable generator stage (3), which comprises a switching spark gap (4) for generating electrical discharges in a gaseous medium and additional electrical components (5-10) for charging and/or discharging the generator stage (3) , wherein the switching spark gap (4) is arranged in the flue (2) with a defined gas exchange for controlling and/or keeping constant a dielectric strength of the gaseous medium, wherein the support structure (2) has a supporting function for the switching spark gap (4) and for at least one of the electrical components (5-10) of the at least one chargeable generator stage (3) , wherein the flue (2) is an insulating tube (2) with a polygonal or round cross section and an impulse capacitor (5), a series resistor (7) and/or a parallel resistor (8) are arranged for each generator stage (3) at the side walls (11) of the insulating tube (2), characterized in that the impulse capacitor (5), the series resistor (7), the parallel resistor (8) and the charge resistor (9) are arranged outside the flue (2) and contacts or lead-throughs (5b) into an interior (22) of the flue are provided.
2. Electrical impulse generator (1) as claimed in claim 1, wherein :
(a) the flue (2) has a supporting function for at least one impulse
capacitor (5) of the at least one chargeable generator stage (3) and/or
(b) the flue (2) has a supporting function for at least one series
resistor (7), parallel resistor (8), charging resistor (9) and/or potential
resistor (10) of the at least one chargeable generator stage (3) and
(c) in particular that the flue (2) forms the supporting frame for
all generator stages (3) of the impulse generator (1).
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3. Electrical impulse generator (1) as claimed in anv one of the
preceding claims, wherein :
(a) the insulating tube (2) has a small cross sectional area for
creating a low inductance spark current circuit with a small enclosed area
and/or
(b) the insulating tube (2) is designed to be assembled from modules
(14) stackable on top of each other, which comprise at least one generator
stage (3), preferably two, three or four generator stages (3).
4. Electrical impulse generator (1) as claimed in any one of the
preceding claims, wherein terminals (4a, 5a, 6a) of the switching spark gap
(4) , the impulse capacitor (5), the series resistor (7) and the parallel resistor (8) are arranged inside the flue (2).
5. Electrical impulse generator (1) as claimed in any one of the
preceding claims, wherein :
(a) the flue (2) is built from insulating plates (11) assembled into
a triangular cylinder assembly (2) and
(b) mounting holes for either mounting the switching spark gap (4),
or an impulse capacitor (5), or two mounting arms (6) for receiving a series
resistor (7) and a parallel resistor (8) are arranged in each side wall
(11), respectively.
6. Electrical impulse generator (1) as claimed in any one of the
preceding claims, wherein :
(a) the insulating plates (11) are linked by metallic bracket members (lla) contacting adjacent terminals (4a, 5a, 6a) of the switching spark gap (4) and the electrical components (5-9), and/or
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(b) the triangular cylinder assembly (2) can be assembled from
triangular cylinder modules (14), which carry at least one generator stage
(3), preferably two, three or four generator stages (3), and are stackable
on top of each other,
(c) in particular that each cylinder module (14) comprises projecting
centering members in staggered relation to a side wall (11), in particular
centering pins glued or mounted to the bracket members (lla), or a centering
frame for stacking the cylinder modules (14).
7. Electrical impulse generator (1) as claimed in any one of the
preceding claims, wherein :
(a) two side walls (11) of the triangular cylinder assembly (2)
comprise projecting parts (12) , each having at least one support hole (13),
in an area, of an impulse capacitor (5) and
(b) in particular that a connecting line through the support holes
(13) run substantially through a center of mass of the impulse generator
(1).
8. Electrical impulse generator (1) as claimed in any one of the
preceding claims, wherein :
(a) the flue (2) comprises viewing windows (4c) for the switching
spark gaps (4) and/or
(b) a drive (4d) for the switching spark gap (4) is arranged in the
flue (2) and/or
(c) where applicable, additional switching spark gaps are also
arranged in the flue (2) .
9. Electrical impulse generator (1) as claimed in any one of the
preceding claims, wherein :
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a) the flue (2) comprises at one end, preferably at a lower end, an air input opening (15a) with a ventilator and at the other end, preferably at an upper end, an air outlet opening (15b),
(b) the support structure and the flue (2) , in particular a flue
forming the support structure (2) , are arranged on a displaceable frame
(16), in particular on a wheeled vehicle or air-cushioned vehicle,and/or

(c) the impulse generator (1) is a Marx impulse voltage generator (1)
or an impulse current generator.
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A integrated flue support construction (2) for a Marx impulse voltage generator (2) with several generator stages (3} is disclosed. It has been known to arrange a flue (2) for flushing the air of switching spark gaps (4) separately from a support frame for the switching spark gaps (4), the impulse capacitors (5) and series and parallel resistors (7,8) .According to the invention/ the flue (2) has a supporting function for the switching spark gaps (4) and individual or all electrical components (5-10) of the impulse circuit. In one embodiment the flue (2) consists of a triangular cylinder support structure (2), wherein the side walls (11) are formed by insulating plates (11), each receiving one of the electrical components, namely the switching spark gap (4), impulse capacitor (5) and resistors (7, 8). Advantages of the invention are : A less complicated construction and a saving of costs, a more compact design with smaller flue cross sectional area (22) and thereby smaller self-inductance of the impulse circuit as well as easier production, transportability and handling because of stacked modules (14) each with at least one generator stage (3).